The present invention relates to a production process for an optical transmitting subassembly. Transmitting subassemblies of the generic type are used for example in beam deflection receptacles for fiber-optic transmitting components or combined transmitting/receiving components. In these transmitting subassemblies, an output bundle of rays is generated by an edge-emitting laser diode and deflected, typically through 90xc2x0, in a first deflection. For this purpose, the laser diode is mounted on a submount, as it is known, on which glass optical prism elements for the deflection of the output bundle of rays from the laser diode are likewise fastened.
FIG. 1 shows an overall view of a fiber-optic transmitting component in longitudinal section along an optical glass fiber 23 coupled to the component. The component has a mounting platform 25, which is preferably fabricated from metal and has a circular through opening on its one long side. On one side of this circular passage opening, a transmitting subassembly 100 is mounted and, on the other side of the circular passage opening, a cut-out is provided into which a tubular part holding a spherical lens 26 and belonging to a beam deflection receptacle 22 projects. The beam deflection receptacle 22 also has a beveled face in the interior, on which a deflection mirror 24 is provided. The transmitting subassembly 10 is mounted on a silicon submount 1 and substantially comprises an edge-emitting semiconductor laser 6 and optical prism elements 2a, 2b and 2c fabricated from glass, between which a highly reflective interface is formed at 45xc2x0 to the laser ray or to the surface of the submount. A bundle of laser radiation emitted by the semiconductor laser 6 is thus deflected through 90xc2x0 at this interface in the direction of the submount 1. The latter is transparent to the laser radiation. The bundle of laser radiation passes through the circular passage opening in the mounting platform 25 and is focused by the spherical lens 26. The bundle of rays then strikes the deflection mirror 24 and is directed by the latter onto the entry surface of the glass fiber 23.
Hitherto, the transmitting subassembly 100 has been produced by the optical prism deflection elements 2a, 2b and 2c being produced individually, placed on the submount 1, aligned with one another and bonded adhesively or anodically. The faces of the optical prism elements were produced by grinding and polishing techniques. A mirror coating was applied to the prism face contributing to the beam deflection. Production processes of this type are known, for example from German published patent application DE 198 10 624 and U.S. Pat. No. 5,875,205 (see, European patent application EP 0 660 467).
That production process proves to be relatively cumbersome, since the optical prism elements 2a and 2b first of all have to be fabricated separately and then have to be fastened to the submount individually in a specific alignment in relation to one another. The expenditure of a relatively large amount of time is therefore necessary for the completion of an individual transmitting subassembly.
U.S. Pat. No. 5,637,885 (German published patent application DE 42 11 899) describes a process for the production of a microsystem, wherein a plurality of wafers are joined to form a wafer composite. In this case, the joining is carried out after the individual wafers have finally been structured.
It is accordingly an object of the invention to provide a fabrication method for an optical transmitter subassembly, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provides for reduced time needed for the production.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of producing an optical transmitting subassembly, which comprises:
a) joining a transparent submount wafer and a glass wafer at their main surfaces;
b) shaping a recess in the glass wafer, the recess having at least one side wall enclosing an angle of substantially 45xc2x0 with the main surface of the submount wafer;
c) mounting a semiconductor laser on the submount wafer such that, during an operation thereof, the laser emits a bundle of rays into the glass wafer in a direction towards the at least one side wall of the recess; and
d) rendering the at least one side wall of the recess highly reflective for the bundle of rays.
In other words, the objects of the invention are achieved with a fabrication process for an optical transmitting subassembly. In the method, first of all a transparent submount wafer and a glass wafer are joined to each other at their main surfaces, then a recess is shaped in the glass wafer, having at least one side wall which substantially forms a 45xc2x0 angle with the surface of the submount wafer, a semiconductor laser is then mounted on the submount wafer in such a way that during operation it emits a bundle of rays into the glass wafer in the direction of the at least one side wall of the recess, and the at least one side wall of the recess is acted on in such a way that it becomes highly reflective for the bundle of rays.
Therefore, according to the invention, the joining of a submount wafer and of a glass wafer is carried out without already structured faces being present on the glass wafer. Structuring of the glass wafer is carried out only after it has been joined to the submount wafer.
The transparent submount wafer preferably consists of a material of relatively high thermal conductivity, so that it exhibits the properties of a heat sink.
In a preferred exemplary embodiment, a V-shaped recess is shaped in process step b) and, in process step d), at least one of the mutually opposite side walls of the V-shaped recess is acted on in the manner described. For this purpose, it proves to be advantageous if the mutually opposite side walls substantially form a 90xc2x0 angle with each other.
It proves to be expedient and advantageous if, before process step a), recesses are shaped, for example by means of wet chemical etching, at a suitable point into the main surface of the glass wafer that is to be joined to the submount wafer, so that the glass wafer is subsequently not joined to the submount wafer in the area of these recesses in process step a). As a result, after process step a) or process step b), the areas of the glass wafer which are located over the recesses and not needed can then be removed relatively easily, preferably by sawing.
The V-shaped recess can advantageously be shaped by a V-shaped groove being produced in the glass wafer by means of a V-shaped saw blade, such as a parting and grinding blade or the like. In this case, the V-shaped recess can firstly be pre-sawn with a coarse-grained parting and grinding blade and then re-sawn with a fine-grained parting and grinding blade.
In an advantageous exemplary embodiment, which is still to be explained, only two prism-like optical glass elements still remain standing on the submount wafer after the sawing steps outlined have been carried out.
In process step d), a rod-like element with a substantially right-angled triangular cross section and having a horizontal upper supporting face is introduced into the V-shaped recess. Before the introduction of the rod-like element, one of its equilateral side walls is provided with a reflective coating. The rod-like element is firstly shaped as a rod with a rectangular cross section and then, before or after introduction into the V-shaped recess, an area of the rod on the side facing away from the submount wafer is removed in such a way that a horizontal supporting face is formed. This face can be used to arrange an optical receiver on it, so that the transmitting subassembly can be used in a combined transmitting/receiving component.
A rod with a rectangular cross section can be obtained, for example, by a glass wafer being provided with a reflective coating on one main surface and being divided up into a number of rods.
The submount wafer is preferably formed by a semiconductor wafer, in particular a silicon wafer, if it is sufficiently transparent for the necessary wavelength.
As already described, it may be necessary at an arbitrary time after process step a) has been carried out, for sections of the submount wafer outside the beam deflection section to be shaped or already shaped to be exposed by removing appropriate areas of the glass wafer, preferably those areas which are situated over the shaped recesses, in order that the semiconductor laser and, if appropriate, a monitor diode can be mounted on these sections of the submount wafer.
In accordance with another feature of the invention, in the shaping operation of the recess in step b), the glass wafer is severed.
In accordance with a concomitant feature of the invention, the semiconductor laser is mounted in step c) such that the bundle of rays of the laser is emitted parallel to the surface of the submount wafer.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a production process for an optical transmitting subassembly, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.